0, 1, 2, and 3-Dimensional zinc oxides enabling high-efficiency OLEDs

•ZnO nanostructures synthesized in 0D, 1D, 2D, and 3D forms.•Doped ZnO in PEDOT:PSS significantly enhances hole mobility in hole-injection layers.•The synergistic effects of different ZnO nanostructures in enhancing charge injection properties, leading to superior OLED efficiency.•This work demonstrated how tailoring the dimensions and synthesis conditions of ZnO nanostructures can optimize their performance for OLED applications.•1D-ZnO nanowires doped in PEDOT:PSS led to substantial PE, CE, and EQE enhancements (46%, 54%, and 64%). In the pursuit of high-efficiency organic light-emitting diodes (OLEDs), this paper unveils the potential of zinc oxide (ZnO) nanostructures of various dimensions (0,1,2, and 3D), doped in hole injection layer (PEDOT:PSS). Unique enhancements were demonstrated in forms from nanoparticles (0D) to nanowires (1D), nanosheets (2D), and nanoflowers (3D), revolutionizing OLED performance. Specifically, the incorporation of 0D-ZnO doped in PEDOT:PSS resulted in remarkable efficiency improvements of 19 % in maximum power efficacy (PEmax), 19 % in maximum current efficacy (CEmax) and 24 % in maximum external quantum efficiency (EQEmax), compared with the undoped counterpart. Elevating the dimensions to 1D-ZnO (20 nm), when doped in PEDOT:PSS, enabled an increment of 46, 54 and 64 % in PEmax, CEmax and EQEmax, respectively. Furthermore, 2D-ZnO (annealed at 400 °C) doped in PEDOT:PSS achieved notable performance improvements, with enhancements of 24 % in PEmax, 23 % in CEmax, and 28 % in EQEmax. Despite size limitations, 3D-ZnO doped in PEDOT:PSS exhibited enhancements of 11 % in PEmax, 15 % in CEmax, and 20 % in EQEmax. We achieved the best results by integrating 1D-ZnO into PEDOT:PSS, which may be attributed to the small diameter of the 1D-ZnO structure when compared to 0D, 2D, and 3D ZnO, resulting in superior OLED performance. These findings demonstrate the significant potential of ZnO nanostructures doped in PEDOT:PSS in enhancing the performance of green OLEDs, and paving the way for more sustainable, cost-effective, and efficient OLEDs for display and lighting applications. Continued research on ZnO and other inorganic materials holds promise for further advancements in OLED technology and a brighter, more energy-efficient future.